1. Field of the Invention
The invention relates to a private branch exchange which can cope with services of the ISDN.
2. Related Background Art
According to a conventional private branch exchange, when a call is received from an ISDN line, all of digital terminals which have been preset in correspondence to the line are allowed to ring. When a call is received from an analog line, all of analog terminals which have been preset in correspondence to the line are allowed to ring.
In the conventional private branch exchange, therefore, even when a transmission terminal notifies information indicating that it wants to execute a communication as a telephone through the ISDN, not only-the digital telephones but also the G4 facsimiles are allowed to ring. Consequently, when the G4 facsimile responds to a call reception, the communication cannot be performed.
On the other hand, in the conventional private branch exchange, even when a transmission terminal notifies information indicating that it wants to perform a data communication through the ISDN, not only the G4 facsimiles but also the digital telephones which can perform only the communication are allowed to ring. Therefore, when such a digital telephone responds to a call reception, the data communication cannot be performed.
In the conventional private exchange, when a G3/G4 facsimile having both of the G3 and G4 functions is connected to an extension digital interface, in the case where a call is received from the G3 facsimile through the analog line, the G3/G4 facsimile cannot be allowed to respond to the call reception.